In comments and logs, say "UTC" not "GMT"

Fix for #6113.

Note that the RFC1123 times we generate still all say 'GMT'.  I'm
going to suggest this is not worth changing.

src/or/confparse.h

@@ -23,7 +23,7 @@ typedef enum config_type_t {
   CONFIG_TYPE_BOOL,         /**< A boolean value, expressed as 0 or 1. */
   CONFIG_TYPE_AUTOBOOL,     /**< A boolean+auto value, expressed 0 for false,
                              * 1 for true, and -1 for auto  */
-  CONFIG_TYPE_ISOTIME,      /**< An ISO-formatted time relative to GMT. */
+  CONFIG_TYPE_ISOTIME,      /**< An ISO-formatted time relative to UTC. */
   CONFIG_TYPE_CSV,          /**< A list of strings, separated by commas and
                               * optional whitespace. */
   CONFIG_TYPE_LINELIST,     /**< Uninterpreted config lines */

src/or/hibernate.c

@@ -890,12 +890,12 @@ hibernate_end_time_elapsed(time_t now)
       /* We weren't sleeping before; we should sleep now. */
       log_notice(LD_ACCT,
                  "Accounting period ended. Commencing hibernation until "
-                 "%s GMT", buf);
+                 "%s UTC", buf);
       hibernate_go_dormant(now);
     } else {
       log_notice(LD_ACCT,
              "Accounting period ended. This period, we will hibernate"
-             " until %s GMT",buf);
+             " until %s UTC",buf);
     }
   }
 }

src/or/networkstatus.c

@@ -775,7 +775,7 @@ router_set_networkstatus_v2(const char *s, time_t arrived_at,
     long delta = now - ns->published_on;
     format_time_interval(dbuf, sizeof(dbuf), delta);
     log_warn(LD_GENERAL, "Network status from %s was published %s in the "
-             "future (%s GMT). Check your time and date settings! "
+             "future (%s UTC). Check your time and date settings! "
              "Not caching.",
              source_desc, dbuf, published);
     control_event_general_status(LOG_WARN,
@@ -1874,7 +1874,7 @@ networkstatus_set_current_consensus(const char *consensus,
     format_iso_time(tbuf, c->valid_after);
     format_time_interval(dbuf, sizeof(dbuf), delta);
     log_warn(LD_GENERAL, "Our clock is %s behind the time published in the "
-             "consensus network status document (%s GMT).  Tor needs an "
+             "consensus network status document (%s UTC).  Tor needs an "
              "accurate clock to work correctly. Please check your time and "
              "date settings!", dbuf, tbuf);
     control_event_general_status(LOG_WARN,

src/or/statefile.c

@@ -416,7 +416,7 @@ or_state_save(time_t now)
   format_local_iso_time(tbuf, now);
   tor_asprintf(&contents,
                "# Tor state file last generated on %s local time\n"
-               "# Other times below are in GMT\n"
+               "# Other times below are in UTC\n"
                "# You *do not* need to edit this file.\n\n%s",
                tbuf, state);
   tor_free(state);